Most people that know the name Mario Mendoza today know him for his hitting, but not in the way that he probably wants people to remember him. Used mostly as a defensive sub, Mendoza went to bat 173 times in his rookie year in Pittsburgh, put up a .510 OPS and never again cracked 100 plate appearances with the Pirates.
It could have ended there, just another (incredibly) light hitting middle infielder who got a few seasons and then faded into history's dustier pages. But Mendoza wanted out of Pittsburgh. Maybe it was because he couldn't see how feeble he was at the plate and wanted more playing time. Maybe he thought it was smelly. Who knows? Still, asking for a trade in the winter before the 1979 season, the Pirates shipped Mendoza to Seattle with Odell Jones (sucked) and Rafael Vasquez (sucked) in exchange for Rick Jones (never played another MLB game), Tom McMillan (ditto) and Enrique Romo, who had two good years as a relief pitcher.
By the way, that next season the Pirates won the World Series. Good move, Mario.
In his first season as a Mariner, Mendoza reached a career high in playing time, appearing in 148 games and netting 401 plate appearances. He would walk or be hit by a pitch ten times and ground into 12 double plays, a feat done by only 60 other players since World War II. For the year, Mendoza posted an incredible .198/.216/.249. That .466 OPS amounted to an OPS+ (park-adjusted) of 25.
It marks the worst single season hitting performance in Mariner history and the 11th worst in baseball history since 1961. Brian Hunter's was worse after you account for his position --he played left field, Mendoza was a short stop-- but independent of where he played in the field, nobody was even close to Mendoza's negative impact at the plate. Hunter's awful hitting line was 27.5 runs below league average. Mendoza's came out to -36.5 below average, a full nine runs worse.
For context, Jose Lopez's past season weighed in at -23 runs against average and that took over 200 additional trips to the plate to reach. Mendoza would somehow get another 300 trips to the plate the following year and improve to a .245/.286/.310 line before the Mariners traded him to Texas in an 11-player trade notable only for the departure of Rick Honeycutt, who was somewhat decent, to the Rangers. It was such a bad deal that it would single-handedly cause the 1981 strike.*
Mario Mendoza's absolute futility at hitting helped give rise to the phrase The Mendoza Line, which commonly refers to a .200 batting average. We probably will never get a .300 batting average named after Ichiro, but at least the Mariners have ties to the .200 line already sewn up. Too bad, Miguel. Mario Mendoza, owner of the single worst hitting season in Mariner history and namesake of most ignominious references in baseball.